Sohl U.S. Pat. No. 3,562,366 shows a method of repairing a composite glass windshield by subjecting the area to supersonic vibration applied in a series of short bursts. Hollingsworth U.S. Pat. No. 3,765,975 also shows a method of repairing such a windshield by applying alternate negative and positive pressures with a maximum pressure not exceeding about 135 psi. Forler et al. U.S. Pat. No. 3,841,932 shows a method of treating a cracked windshield through the use of a hand-held probe by means of which pressure is applied to the apex of the cone in all angular positions and continuously changing directions thereby causing the cone to gyrate.
Referring to Sohl and Hollingsworth, these patents require special apparatus which is expensive and difficult to operate because they largely conceal the point of contact with the cone. Forler et al on the other hand specifies a hand-held probe and that the probe be moved in all angular directions which could thus readily rub against the edges of the crack and cause the same to spread and enlarge.